There are a broad number of applications where it is useful to be able to determine the position of one element relative to another element and/or the absolute position of a moveable element. As one example, hydraulic and pneumatic linear actuators typically include an elongated body with a drive rod or element that extends from and retracts into the body. It is often useful to know the position of this drive rod so as to control the position of a machine element attached to the drive rod. Various sensing systems are available for sensing the position of the drive rod. For example, a linear or rotary position sensor may be attached to the drive rod or an element attached to the drive rod. However, these sensors typically are external add-on systems with a variety of limitations. As such, there is a need for additional sensing systems and actuators incorporating such systems.
There are also a variety of other mechanical systems where position sensing is useful. As an example, a linear motion bearing may be moveable along an elongated rod or shaft and may support portions of a mechanical system. A measurement of the position of this linear bearing along the rod or shaft may be useful in determining the position of various elements, whether a system is within specifications, when to turn actuators and/or motors on or off, and for other reasons. Again, there are a number of sensing systems available for this use, but there remains a need for additional systems.